The aim of the proposed research is to investigate the role of the chest wall and the distribution of ventilation in the lung. Two approaches will be used: 1) Expansion of the rib cage increases the magnitude of changes in negative pleural pressure (delta P) and thereby inflates the lung. The relationships between rib cage expansion, delta P, and lung inflation (V in) will be examined when the rib cage is impeded, thereby altering delta P and lung inflation. The effects on delta P and on the distribution of V in will be assessed when the lower rib cage, a hemithorax, and the anterior or lateral portion of the rib cage are prevented from expanding. 2) The diaphragm expands the rib cage and should thereby affect ventilation to the lung bases. The role of this coupling between the diaphragm an the rib cage on the distribution of ventilation in the lung will be investigated when the diaphragm is unable to expand the rib cage and when descent of the diaphragm is prevented, thereby converting all of its contraction into rib cage expansion. Rib cage expansion is impeded by a specially designed restraining device surrounding the rib cage. Diaphragmatic descent is prevented by an inextensible binder surrounding the abdomen. The effects on delta P and, therefore, on the ventilation of the portion of lung affected by this delta P, will be assessed by measuring the distribution of inspired boluses of 133Xenon with scintillation counters. This distribution will be correlated with concurrent measurements of changes in chest wall and abdominal dimensions to obtain an index of the interrelationship between changes in chest wall shape, delta P and ventilation of the underlying lung.